libsaria: Manually set artwork through a copy_in_file() function

I created this function in the cache to make a generic way to copy
outside files into the cache tree.  It makes sense to do this in the
cache, since I want to keep everything self-contained.

libsaria/path/lastfm.py

@@ -77,7 +77,4 @@ def get_artwork(file):
 	threads.background(get_album_art, file)
 
 def set_artwork(artist, album, img_path):
-	file = cache.open_file(artist, album, "Folder.jpg")
-	new_img = open(img_path)
-	file.write(new_img.read())
-	file.close()
+	cache.copy_in_file(artist, album, "Folder.jpg", img_path)

libsaria/storage/cache.py

@@ -37,6 +37,9 @@ def get_item(artist, album, title, file, cache_func):
 		cache_path = fill_cache(artist, album, title, cache_func, cache_path)
 	return cache_path
 
-def open_file(artist, album, file):
+def copy_in_file(artist, album, file, orig_file):
 	cache_path = make_cache_path(artist, album, file)
-	return open(cache_path, 'w')
+	orig = open(orig_file)
+	f = open(cache_path, 'w')
+	f.write(orig.read())
+	f.close()